Understanding medical equipment backup sizing
Why this tool includes a mandatory safety framing
This calculator is built for planning purposes and general household backup, not as a substitute for a medically verified backup power plan. For any life-sustaining device, redundancy matters more than optimization: a dedicated medical backup battery or generator recommended by your equipment supplier should exist independently of a home solar battery system. Use this tool to understand rough scale, then work with medical equipment professionals on the actual plan.
Why margin matters more here than in other sizing tools
Most battery sizing tools on this site use standard depth of discharge and efficiency assumptions without extra padding, since a slightly undersized system for general home backup is an inconvenience. For medical equipment, undersizing carries real health risk, which is why this tool includes an explicit safety margin option on top of the standard efficiency losses. A 20 to 30% margin accounts for battery aging over time, colder temperatures reducing usable capacity, and normal device wear, consistent with Ready.gov's guidance for people who depend on electricity and medical devices.
What utility medical baseline programs offer
Many utilities maintain a medical baseline, critical care, or life support customer registry that provides earlier outage notification, sometimes a lower electricity rate, and in some cases priority restoration for documented life-sustaining equipment. Registering with your utility is a free step that complements, rather than replaces, having battery backup in place, and the potential rate reduction is worth factoring into the quick financing comparison tool in our Financing category when weighing overall system cost. The wildfire PSPS planning tool covers a related scenario where advance outage notice matters most.
Why battery aging matters for repeat medical use
Lithium batteries lose a small percentage of their capacity each year of use, typically 1 to 3% annually depending on chemistry and usage patterns, consistent with the gradual capacity fade NREL accounts for over its assumed 15-year system lifespan in the Annual Technology Baseline. A battery sized exactly to today's need may fall short in 3 to 5 years without the safety margin this tool builds in. The round trip efficiency calculator covers a related capacity-loss factor in more depth.
What to do with this number next
Take this planning number to your equipment supplier and a licensed solar installer together, since medical equipment backup often benefits from professional input on both the medical and electrical sides. The battery inverter pairing tool is a useful next step to confirm your inverter can reliably start and run the device. The inverter's surge and continuous rating for this specific device is covered in the inverter continuous vs peak rating calculator in our Inverters & Equipment category.